Improving both activity and stability for direct conversion of cellulose to ethanol by decorating Pt/WOx with mononuclear NbOx†

Abstract

Chemocatalytic conversion of cellulose to ethanol provides an alternative route for biofuel production with a theoretical carbon yield of 100%; however, it faces significant challenges of high catalyst cost and poor catalyst stability. In this work, we report a new strategy to decrease the use of expensive noble metals, by decorating mononuclear NbO_x on a low-Pt Pt/WO_x catalyst surface. The resulting 0.1Nb/0.5Pt/WO_x catalyst gave rise to an ethanol yield of 33.7% together with an ethylene glycol yield of 21.8%, and the noble metal efficiency reached 25.90 g_ethanol g_Pt⁻¹ h⁻¹, an increase by a factor of 2–10 compared to those in the literature. Moreover, the catalyst stability was significantly enhanced by the decoration of mononuclear NbO_x, allowing for recycling at least 7 times without obvious activity decay. Characterization revealed that Pt was highly dispersed at subnanometer and single atom scales, and modification with mononuclear NbO_x facilitated hydrogen spillover and created more oxygen vacancies on the WO_x surface upon hydrogen reduction, thus generating a higher density of Brønsted acid sites. This effect not only favored cellulose conversion to ethylene glycol but also promoted the hydrogenolysis of ethylene glycol to ethanol.